Forging is a process by which the shape and physical properties of metal can be changed. The process involves placing a piece of metal (normally heated) between the halves of a die and forcing the die to close by impact or pressure. The operation causes a controlled plastic deformation of the metal into the cavities of the die. This flow of material results not only in a change in shape of the metal but also increases the density and uniformity of the metal, improves its grain structure, and causes a shape-conforming grain flow. The resulting workpiece has properties which are superior to those generated by other methods, making forging essential where high performance workpieces are required.
One of the critical components of a forging system is the lubricant which separates the die from the workpiece. As with all lubricating situations, it is essential that this lubricant be effective to minimize wear of the extremely expensive forging dies and minimize expenditure of energy over a wide range and condition. Somewhat peculiar to the forging process, however, is that merely maximizing lubricity is not the only goal, since a certain degree of friction between the workpiece and die is essential to optimize the properties of the workpiece. This controlled lubricity is particularly important when it is necessary to fill deep impression dies.
As modern demand for safer and more dependable machine structures increases, the forging art is being applied to more difficult materials, at higher temperatures and pressures to form more complex shapes. Although oil-based lubricating compositions, which are effective under these extreme conditions, have been developed, their properties are found to conflict seriously with national commitments to personal safety and protection of the environment. The oil-based lubricants are normally flammable and can ignite well below common operating temperatures. Normal operation results in billowing carbonaceous smoke which is unpleasant and sometimes toxic. Furthermore, cleaning of the workpieces and dies requires solvent washes that produce large quantities of rinse which, because of the economics of recycling, and desire to protect the environment can present serious disposal problems.
Attempts at avoiding the problems inherent in the use of oil-based lubricants have generally been directed toward water-based compositions. Early attempts, involving mixtures of graphite, clay minerals, and molybdenum disulfide, were found ineffective, because they did not sufficiently wet the hot metal surfaces to provide lubrication. They were also unacceptable due to the corrosion caused by the high temperature break-up of the components. Additives and substitutions which solved one problem often created another. For example, the addition of soaps to improve wetting often caused caking in cavities and increased smoke production and odor. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a forging lubricant which effectively reduces the die wear and energy of requirement of a forging operation.
Another object of this invention is the provision of a forging lubricant which produces an extremely low amount of air pollution.
A further object of the present invention is the provision of a forging lubricant which is simple and easy to produce and which, in use, leads to relatively less expense in overall operating costs.
It is another object of the instant invention to provide a forging lubricant which has a long storage life and is not adversely effected by reasonable storage conditions.
A still further object of the invention is the provision of a forging lubricant which is simple and safe to apply to the dies using spray equipment.
It is a further object of the invention to provide a forging lubricant which is virtually non-flamable and does not give off undesirable vapors or corrosive byproducts during use.
It is a still further object of the present invention to provide a forging lubricant which has the proper combination of lubricating properties to allow predictable and effective operation of forging technique over wide ranges of workpiece shape, temperature, pressure and material.
Another object of the invention is the provision of a forging lubricant which has adequate insulating properties to prevent undesirable cooling of the workpiece by the dies.
Another object of the invention is the provision of a forging lubricant which effectively prevent workpieces from sticking in the dies after the forging operation.
Another object of the invention is the provision of a forging lubricant which is easily cleaned from the workpiece and dies, and which results in a rinse which can be easily cleaned to avoid pollution.